Reproducible and highly miniaturized bazooka RF Balun using a printed capacitor.

PURPOSE: There is currently a strong trend in developing RF coils that are high-density, lightweight, and highly flexible. In addition to the resonator structure of the RF coil itself, the balun or cable trap circuit serves as another essential element in the functionality and sensitivity of RF coils. This study explores the development and application of reproducible highly miniaturized baluns in RF coil design. METHODS: We introduce a novel approach to producing Bazooka baluns with printed coaxial capacitors, enabling the achievement of significant capacitance per unit length. Rigorous electromagnetic simulations and thorough hardware fabrication validate the efficacy of the proposed design across various magnetic field strengths, including 1.5 T, 3 T, and 7 T MRI systems. RESULTS: Bench testing reveals that the proposed balun can achieve an acceptable common-mode rejection ratio even when it is highly miniaturized. The use of printed capacitors allows for a notable reduction in balun length and ensures high reproducibility. Findings demonstrate that the proposed balun exhibits no RF field distortion even when placed close to the sample, making it suitable for flexible coils, wearable coils, and high-density coils, particularly in high-field MRI. CONCLUSION: The reproducibility inherent in the manufacturing process of printed coaxial capacitors allows for simple fabrication and ensures consistency in production. These advancements pave the way for the development of flexible coils, wearable coils, and high-density coils.

Quantitative analysis of soil potassium by near-infrared (NIR) spectroscopy combined with a three-step progressive hybrid variable selection strategy.

Soil potassium is a crucial nutrient element necessary for crop growth, and its efficient measurement has become essential for developing rational fertilization plans and optimizing crop growth benefits. At present, data mining technology based on near-infrared (NIR) spectroscopy analysis has proven to be a powerful tool for real-time monitoring of soil potassium content. However, as technology and instruments improve, the curse of the dimensionality problem also increases accordingly. Therefore, it is urgent to develop efficient variable selection methods suitable for NIR spectroscopy analysis techniques. In this study, we proposed a three-step progressive hybrid variable selection strategy, which fully leveraged the respective strengths of several high-performance variable selection methods. By sequentially equipping synergy interval partial least squares (SiPLS), the random forest variable importance measurement (RF(VIM)), and the improved mean impact value algorithm (IMIV) into a fusion framework, a soil important potassium variable selection method was proposed, termed as SiPLS-RF(VIM)-IMIV. Finally, the optimized variables were fitted into a partial least squares (PLS) model. Experimental results demonstrated that the PLS model embedded with the hybrid strategy effectively improved the prediction performance while reducing the model complexity. The RMSET and RT on the test set were 0.01181% and 0.88246, respectively, better than the RMSET and RT of the full spectrum PLS, SiPLS, and SiPLS-RF(VIM) methods. This study demonstrated that the hybrid strategy established based on the combination of NIR spectroscopy data and the SiPLS-RF(VIM)-IMIV method could quantitatively analyze soil potassium content levels and potentially solve other issues of data-driven soil dynamic monitoring.

Typical Atrioventricular Nodal Re-Entry Tachycardia Masquerading as Atrial Fibrillation.

We report 3 cases of irregular, narrow complex tachycardia misdiagnosed and treated for atrial fibrillation. The adenosine response, detection of recurring triple cycle length variation patterns, and pseudo-R-wave in lead V1 during tachycardia made us suspect typical atrioventricular nodal re-entrant tachycardia. The electrophysiology study confirmed atrioventricular nodal re-entrant tachycardia, and symptoms were resolved by slow pathway modification.

A Computational Study on Effects of PID Temperature Target and RF Frequency for PID-Controlled Nonablative RF Cosmetic Systems.

BACKGROUND AND OBJECTIVES: Commonly adopted in cosmetic dermatology, nonablative radiofrequency (RF) devices convert high-frequency electromagnetic energy into thermal energy to induce a wound-healing response in skin tissue. However, differences in the electrical properties of different skin layers raise questions about the impact of different RF frequencies and target temperatures on treatment effectiveness. This paper presents a finite element analysis (FEA)-based computational study aimed at simulating and optimizing the effects of a proportional integral derivative (PID)-controlled RF cosmetic devices under different combinations of these two parameters during treatment. STUDY DESIGN/MATERIALS AND METHODS: A 3D physical model for the application of a nonablative RF device was constructed using COMSOL, which included the human tissue and RF electrodes, electromagnetic and thermal boundary conditions, as well as the PID controller. FEA was performed for each of the twelve models with parameter combinations of three RF frequencies (0.1, 0.5, and 1 MHz) and three PID-controlled target temperatures (60°C, 65°C, and 70°C) plus one group without PID control. Treatment effectiveness was quantitatively assessed using the integration of tissue thermal damage fraction, i.e., thermal damage volume. RESULTS: In the earlier stage of heating (0-10 s), higher RF frequency resulted in a larger thermal damage volume. At 10 s, among models with a temperature target of 70°C, there is a 6.04% difference between the thermal damage volume at RF frequencies of 1.0 and 0.1 MHz. In the later stage of heating(11-80 s), the impact of RF frequency decreases. The difference in thermal damage volume caused by higher temperature targets is more significant, at 80 s, among models with an RF frequency of 1.0 MHz, the 70°C model produces 1.15 and 1.36 times more tissue thermal damage than the 65°C and 60°C models. CONCLUSION: PID controller has ensured treatment safety and uniformity, in exchange for some efficiency. Among 12 parameter combinations, the one with a temperature of 70°C and RF frequency of 1.0 MHz achieved the highest thermal damage volume, which could potentially result in the best esthetic effect. Considering users' different susceptibility to heat, engineers or physicians can select better temperature targets and RF frequencies to bring the desired cosmetic results based on thermal damage volume curves from this study.

Radiofrequency-transparent local B0 shimming coils using float traps.

PURPOSE: Static field (B0) inhomogeneities present a major challenge in high-field MRI. Multicoil shimming using independent, local, direct-current (DC) shim coils has emerged as a powerful and flexible technique to address this issue. However, many-turn DC coils can lead to significant mutual coupling with radiofrequency (RF) coils, causing transmit field (B1 +) distortions and signal-to-noise ratio degradation. METHODS: We introduce an innovative RF-transparent DC coil that performs B0 shimming while minimizing RF performance impact. The design incorporates float traps to maintain high RF impedance, allowing flexible placement relative to the RF coil without compromising signal-to-noise ratio or affecting B1 +. We fabricated square-shaped DC coils with float traps for 3T MRI and compared them with conventional DC coils. To demonstrate high ΔB0/Amp efficiency, we conducted a B0 shimming experiment around a metal hip implant. RESULTS: Bench tests and MRI experimental results demonstrated that the RF-transparent DC coil effectively minimized RF interference, preserved signal-to-noise ratio, and maintained B1 +, even when placed near the RF receive coil. Additionally, the DC coil significantly improved B0 homogeneity near metal implants and substantially reduced image distortion. CONCLUSION: The RF-transparent DC coil offers a flexible, effective solution for managing B0 inhomogeneities, paving the way for integrating multiturn DC coils in clinical MRI settings without extensive hardware modifications.

Evaluating the performance of machine learning and variable selection methods to identify document paper using infrared spectral data.

Infrared spectroscopy is a valuable tool for forensic examinations because it realizes nondestructive and rapid analysis. Recent advancements in machine learning have facilitated the development of chemometrics, extending to applications in questioned document examination. In this study, support vector machine (SVM), feedforward neural network (FNN), and random forest (RF) models were constructed using the infrared spectral data of document paper samples to identify the manufacturer of document paper products. For model training, the infrared (IR) spectral regions were selected based on their variable importance as determined by the RF models. Narrowing the IR spectral data within the range of 1500-800 cm-1 (selected according to variable importance measures) proved effective in terms of enhancing model performance while minimizing computational costs. The FNN and RF models trained on the second-derivative IR spectra in this range obtained F1-scores of 0.978 and 1.000, respectively. The findings of this study confirm the potential of machine learning methods for extracting and examining forensic features in document paper, resulting in robust models with low computational overhead.

An array of paired folded-end dipoles for whole-brain imaging at 9.4 T.

PURPOSE: To improve transmit B1+ field homogeneity and longitudinal coverage of a human head RF array, we developed a novel eight-element transceiver (TxRx) array using composite elements based on paired folded-end dipoles. METHODS: The developed array consisted of eight pairs of coupled folded-end dipoles. Only one dipole in each pair was driven during transmission, while the other was passively coupled with the active one. The distribution of the transmit B1+ field was numerically optimized by changing the overlap between the dipoles and the value of the reactive lumped element placed in the middle of the passive dipole. RESULTS: The proposed array of paired folded-end dipoles substantially improved the B1+ homogeneity and longitudinal coverage over the entire brain including the brain stem compared to a single-row folded-end dipole array. The improved whole brain coverage was demonstrated both numerically and experimentally. CONCLUSION: As a proof of concept, we developed and characterized both numerically and experimentally a prototype of a single-row eight-element 9.4 T array for human brain imaging consisting of composite array elements based on paired passively-coupled folded-end dipoles. The array improved the transmit magnetic field distribution due to the laterally elongated field pattern created by one active and one passive dipole per channel. As a result, the provided coverage was substantially better than that of an 8-element dipole array consisting of long folded-end dipoles. For the first time, an image of the entire human brain at 9.4 T, covering the brain stem up to the fourth vertebra, was obtained using a simple single row eight-element array.

Machine learning for urban land use/ cover mapping: Comparison of artificial neural network, random forest and support vector machine, a case study of Dilla town.

The ability to accurately classify land use/cover (LULC) is critical for environmental monitoring and land use planning. This study compares three machine learning algorithms: Artificial Neural Network (ANN), Support Vector Machine (SVM), and Random Forest (RF) for LULC classification using Google Earth images from the years 2006, 2014, and 2022. The objective of this study is to evaluate and identify the best classifier for LULC classification and change detection. Four LULC categories (Built-up, Open area, Farmland, and Agroforestry) were identified. The evaluation criteria included overall accuracy, kappa coefficient, producer's accuracy, user's accuracy, computing time, algorithm stability, and visual quality. The results showed that the RF algorithm outperformed both SVM and ANN algorithms with an average overall accuracy of 0.97, kappa coefficient of 0.98, producer's accuracy of 0.99, and user's accuracy of 0.97, surpassing the accuracies achieved by SVM (0.96, 0.97, 0.98, and 0.97) and ANN (0.89, 0.81, 0.94, and 0.88), with corresponding computing times of 6.33, 15, and 30 s. All classifiers performed stably with different training sizes. Visual quality assessment revealed that RF had the highest precision. Consequently, the built-up change detection result shows, the net change in built-up area between 2006 and 2022 was increased by 0.74 Km2 for ANN, 1.74 Km2 for SVM, and 1.66 Km2 for RF. The comparison reveals that the RF algorithm showcasing high precision in detecting change, consistent with the data (increased by 1.65 Km2 ) obtained from Dilla town land administration office. To validate the results, the study considered field surveys, reference images, local experts, and previous studies. Based on the findings, the study concludes that using RF classifier with an object-based approach is an effective way to map LULC and detect changes in the study area over time. Future researchers are recommended to utilize this effective algorithm for addressing LULC related problems in the study area.

The effect of T. aestivum chromosomes 1A and 1D on fertility of alloplasmic recombinant (H. vulgare)-T. aestivum lines depending on cytonuclear compatibility.

The effect of T. aestivum L. chromosomes 1A and 1D on fertility of recombinant bread wheat allolines of the same origin carrying the cytoplasm of barley H. vulgare L. and different levels of cytonuclear compatibility was studied. Alloline L-56 included mainly fully sterile (FS) and partially sterile (PS) plants, alloline L-57 included partially fertile (PF) plants and line L-58 included fertile (F) ones. Analysis of morphobiological traits and pollen painting indicated complete or partial male sterility in plants of allolines L-56 and L-57. To differentiate genotypes with cytonuclear coadaptation and genotypes with cytonuclear incompatibility, PCR analysis of the 18S/5S mitochondrial (mt) repeat was performed. Heteroplasmy (simultaneous presence of barley and wheat mtDNA copies) was found in FS, PS, PF and some F plants, which was associated with a violation of cytonuclear compatibility. Wheat-type homoplasmy (hm) was detected in the majority of the fertile plants, which was associated with cytonuclear coadaptation. The allolines used as maternal genotypes were crossed with wheat-rye substitution lines 1R(1A) and 1R(1D). In F1, all plants of PF×1R(1A) and PF×1R(1D) combinations were fertile, and in F2, a segregation close to 3 (fertile) : 1 (sterile) was observed. These results showed for the first time that chromosomes 1A and 1D carry one dominant Rf gene, which controls the restoration of male fertility of bread wheat carrying the cytoplasm of H. vulgare. All plants of F1 combinations FS×1R(1A), FS×1R(1D), PS×1R(1A), PS×1R(1D) were sterile, which indicates that a single dose of genes localized on wheat chromosomes 1A or 1D is not enough to restore male fertility in FS and PS plants. All plants of hybrid combinations F(hm)×1R(1A) and F(hm)×1R(1D) in both F1 and F2 were fertile, that is, fertility of allolines with cytonuclear coadaptation does not depend on wheat chromosomes 1A and 1D.

A deep brain stimulation-conditioned RF coil for 3T MRI.

PURPOSE: To develop and test an MRI coil assembly for imaging deep brain stimulation (DBS) at 3 T with a reduced level of local specific absorption rate of RF fields near the implant. METHODS: A mechanical rotatable linearly polarized birdcage transmitter outfitted with a 32-channel receive array was constructed. The coil performance and image quality were systematically evaluated using bench-level measurements and imaging performance tests, including SNR maps, array element noise correlation, and acceleration capabilities. Electromagnetic simulations and phantom experiments were performed with clinically relevant DBS device configurations to evaluate the reduction of specific absorption rate and temperature near the implant compared with a circular polarized body coil setup. RESULTS: The linearly polarized birdcage coil features a block-shaped low electric field region to be co-aligned with the implanted DBS lead trajectory, while the close-fit receive array enables imaging with high SNR and enhanced encoding capabilities. CONCLUSION: The 3T coil assembly, consisting of a rotating linear birdcage and a 32-channel close-fit receive array, showed DBS-conditioned imaging technology with substantially reduced heat generation at the DBS implants.

The role of a tantalum interlayer in enhancing the properties of Fe3O4 thin films.

High spin polarization and low resistivity of Fe3O4 at room temperature have been an appealing topic in spintronics with various promising applications. High-quality Fe3O4 thin films are a must to achieve the goals. In this report, Fe3O4 films on different substrates (SiO2/Si(100), MgO(100), and MgO/Ta/SiO2/Si(100)) were fabricated at room temperature with radio-frequency (RF) sputtering and annealed at 450 °C for 2 h. The morphological, structural, and magnetic properties of the deposited samples were characterized with atomic force microscopy, X-ray diffractometry, and vibrating sample magnetometry. The polycrystalline Fe3O4 film grown on MgO/Ta/SiO2/Si(100) presented very interesting morphology and structure characteristics. More importantly, changes in grain size and structure due to the effect of the MgO/Ta buffering layers have a strong impact on saturation magnetization and coercivity of Fe3O4 thin films compared to cases of no or just a single buffering layer.

Enhanced NO2 Gas Sensing in Nanocrystalline MoS2 via Swift Heavy Ion Irradiation: An Experimental and DFT Study.

Nanostructured transition metal dichalcogenides (TMDs) like MoS2 hold promise for gas sensing applications due to their exceptional properties. However, limitations exist in maximizing sensor performance, such as limited active sites for gas interaction and sluggish response/recovery times. This study explores swift heavy ion (SHI) irradiation as a strategy to address these challenges in MoS2-based NO2 gas sensors. MoS2 nanoflakes were fabricated and subsequently irradiated with 120 MeV silver (Ag) ions to induce structural and morphological modifications. Characterization techniques confirmed the formation of Mo and S vacancies within the MoS2 lattice due to irradiation. Significantly, SHI irradiation resulted in a remarkable enhancement of approximately 3 times improvement in sensing response compared to pristine MoS2 sensors. Additionally, the irradiated sensors exhibit substantial improvements in both response and recovery times for NO2 detection. SHI irradiation resulted in the formation of self-affine nanostructures and increased grain fragmentation as fluence rises. This enhanced surface area is hypothesized to promote gas-sensor response. To gain deeper insights into the underlying mechanism, first-principles calculations were employed. These calculations suggest that electron transfer occurs from the MoS2 surface to the NO2 molecule during interaction. Furthermore, the irradiation-induced vacancies facilitate stronger NO2 adsorption on the MoS2 surface compared to the pristine sample. This work demonstrates the effectiveness of SHI irradiation in engineering defects within MoS2 nanoflakes, leading to significantly improved NO2 gas-sensing performance. This approach offers a promising avenue for developing next-generation TMD-based gas sensors with enhanced sensitivity, response times, and stability.

Large improvement in RF magnetic fields and imaging SNR with whole-head high-permittivity slurry helmet for human-brain MRI applications at 7 T.

PURPOSE: To optimize the design and demonstrate the integration of a helmet-shaped container filled with a high-permittivity material (HPM) slurry with RF head coil arrays to improve RF coil sensitivity and SNR for human-brain proton MRI. METHODS: RF reception magnetic fields ( B 1 - $$ {\mathrm{B}}_1^{-} $$ ) of a 32-channel receive-only coil array with various geometries and permittivity values of HPM slurry helmet are calculated with electromagnetic simulation at 7 T. A 16-channel transmit-only coil array, a 32-channel receive-only coil array, and a 2-piece HPM slurry helmet were constructed and assembled. RF transmission magnetic field ( B 1 + $$ {\mathrm{B}}_1^{+} $$ ), B 1 - $$ {\mathrm{B}}_1^{-} $$ , and MRI SNR maps from the entire human brain were measured and compared. RESULTS: Simulations showed that averaged B 1 - $$ {\mathrm{B}}_1^{-} $$ improvement with the HPM slurry helmet increased from 57% to 87% as the relative permittivity (εr) of HPM slurry increased from 110 to 210. In vivo experiments showed that the average B 1 + $$ {\mathrm{B}}_1^{+} $$ improvement over the human brain was 14.5% with the two-piece HPM slurry (εr ≈ 170) helmet, and the average B 1 - $$ {\mathrm{B}}_1^{-} $$ and SNR were improved 63% and 34%, respectively, because the MRI noise level was increased by the lossy HPM. CONCLUSION: The RF coil sensitivity and MRI SNR were largely improved with the two-piece HPM slurry helmet demonstrated by both electromagnetic simulations and in vivo human head experiments at 7 T. The findings demonstrate that incorporating an easily producible HPM slurry helmet into the RF coil array significantly enhances human-brain MRI SNR homogeneity and quality at ultrahigh field. Greater SNR improvement is anticipated using the less lossy HPM and optimal design.

Quantitative Estimation of Albedo and Tilt Angle Variation in Bifacial Perovskite Solar Cells.

Bifacial perovskite solar cells (Bi-PSCs) have attracted substantial attention within the photovoltaic (PV) community due to their potential for enhanced power generation, suitability for integration into building structures and applicability in multijunction PV systems. This study presents the fabrication of efficient Bi-PSCs and investigates their unique properties using various characterization techniques, including Lambertian reflection effects through tilt angle arrangements and bottom albedo illuminations. The control device achieved a maximum power conversion efficiency (PCE) of 17.46% under front-side 1 Sun AM1.5G illumination. A significant influence of ground Lambertian reflection is observed with tilt angle variations, resulting in an increase in PCE from 17.46% → 18.82% as the tilt angle reached 20°. Additionally, enhancing the rear-side albedo to 0.5 Sun yielded a maximum PCE of 26% with a bifaciality factor of ∼90% at a tilt angle of 20°. Consequently, the synergistic effect of 0.5 Sun albedo and a 20° angular light inclination led to the development of Bi-PSCs with an efficiency of 26.46%. SCAPS-1D simulations are further employed to validate the experimental Lambertian reflection effects. Moreover, the Bi-PSCs exhibited intrinsic self-encapsulation and chemical robustness (T80 for 2000 h in the N2 atmosphere). This study anticipates that cost-effective and highly efficient Bi-PSCs will emerge as a leading PV technology in both single-junction and tandem PV configurations for electricity generation in the near future.

Parallel transmit hybrid pulse design for controlled on-resonance magnetization transfer in R1 mapping at 7T.

PURPOSE: This work proposes a "hybrid" RF pulse design method for parallel transmit (pTx) systems to simultaneously control flip angle and root-mean-squared B 1 + $$ {\mathrm{B}}_1^{+} $$ ( B 1 rms $$ {B}_1^{\mathrm{rms}} $$ ). These pulses are generally only designed for flip angle, however, this can lead to uncontrolled B 1 rms $$ {B}_1^{\mathrm{rms}} $$ , which then leads to variable magnetization transfer (MT) effects. We demonstrate the hybrid design approach for quantitative imaging where both flip angle and B 1 rms $$ {B}_1^{\mathrm{rms}} $$ are important. THEORY AND METHODS: A dual cost function optimization is performed containing the normalized mean squared errors of the flip angle and B 1 rms $$ {B}_1^{\mathrm{rms}} $$ distributions weighted by a parameter λ $$ \lambda $$ . Simulations were conducted to study the behavior of both properties when simultaneously optimizing them. In vivo experiments on a 7T MRI system with an 8-channel pTx head coil were carried out to study the effect of the hybrid design approach on variable flip angle R 1 $$ {\mathrm{R}}_1 $$ (= 1/T1) mapping. RESULTS: Simulations showed that both flip angle and B 1 rms $$ {B}_1^{\mathrm{rms}} $$ can be homogenized simultaneously without detriment to either when compared to an individual optimization. By homogenizing flip angle and B 1 rms $$ {B}_1^{\mathrm{rms}} $$ , R 1 $$ {\mathrm{R}}_1 $$ maps were more uniform (coefficient of variation 6.6% vs. 13.0%) compared to those acquired with pulses that only homogenized flip angle. CONCLUSION: The proposed hybrid design homogenizes on-resonance MT effects while homogenizing the flip angle distribution, with only a small detriment in the latter compared to a pulse that just homogenizes flip angle. This improved R 1 $$ {\mathrm{R}}_1 $$ mapping by controlling incidental MT effects, yielding more uniform R 1 $$ {\mathrm{R}}_1 $$ maps.

Microneedling With RF-Assisted Skin Penetration Improves the Hard-to-Treat Periorbital Wrinkles: Nonrandomized Clinical Trial.

INTRODUCTION: This prospective study evaluates the efficacy and safety of minimally invasive radiofrequency microneedling (RFMN) for the correction of periorbital wrinkles. This study aimed to address the challenges posed by the periorbital region's unique anatomy and the limitations of existing non-surgical treatments. METHODS: Twenty-four subjects, ranging from 34 to 54 years old with Fitzpatrick skin types II-V, underwent a series of treatments using the Voluderm RF microneedling device. Participants were divided into two groups based on the severity of their wrinkles and treated with customized protocols over four sessions, with a 3-month follow-up to assess outcomes. Efficacy was determined through comparisons of pre-treatment and post-treatment wrinkle severity, using the Lemperle Classification of Facial Wrinkles (LFW) and the Global Aesthetic Improvement Scale, evaluated by both the investigators and the patients. Safety and tolerability were assessed through adverse event reporting and a Visual Analog Scale for treatment discomfort. RESULTS: The results demonstrated a statistically significant reduction in periorbital wrinkle severity, with an average 49% decrease of LFW score and improvements noted across all skin types in both groups. The aggregated facial LFW score decreased from baseline mean 13.00 ± 4.75 to 6.09 ± 3.90 (p < 0.05). The treatment was well tolerated without anesthetics, with minimal downtime and few adverse events, which were transient and resolved without intervention. CONCLUSION: The efficacy of Voluderm RF microneedling in improving periorbital wrinkles of variable severity was demonstrated in patients with diverse skin types. The unique RF-assisted mechanism of the skin penetration granted a high tolerability of the treatments, negligible downtime, and minimum number of adverse events with self-resolution.

Simultaneous multinuclear MRI via a single RF channel.

Magnetic resonance imaging (MRI) stands as one of the most powerful noninvasive and non-destructive imaging techniques, finding extensive utility in medical and industrial applications. Its ability to acquire signals from multiple nuclei grants it additional levels of strength by providing multi-dimensional datasets of the object under test. However, this typically requires dedicated hardware to detect each nucleus. In this paper, we report on the use of a digital lock-in amplifier to perform simultaneous multi-nuclear MRI with a single physical radio frequency (RF) channel. While we showcase this concept by demonstrating the results of fully parallel (TX and RX) 1H and 19F MRI images, we emphasize that it is not limited to two nuclei but can accommodate more nuclei with no extra cost on the hardware or scan time. The scalability is virtually unlimited, constrained only by the processing speed of the digital unit. Furthermore, we demonstrate that the quality of parallel imaging with SNR of 54 is comparable to the commercial single channel with SNR of 43. Thus with no reduction in imaging quality, the proposed concept promises a tremendous reduction in scan time, system complexity, and hardware costs.

Signal-to-noise trade-offs between magnet diameter and shield-to-coil distance for cylindrical Halbach-based portable MRI systems for neuroimaging.

OBJECTIVE: To investigate the trade-off between magnet bore diameter and the distance between the conductive Faraday shield and RF head coil for low-field point-of-care neuroimaging systems. METHODS: Electromagnetic simulations were performed for three different Faraday shield geometries and two commonly used RF coil designs (spiral and solenoid) to assess the effects of a close-fitting shield on the RF coil's transmit and receive efficiencies. Experimental measurements were performed to confirm the accuracy of the simulations. Parallel simulations were performed to assess the static magnet ( B 0 ) field as a function of the magnet bore diameter. The obtainable SNR was then calculated as a function of these two related variables. RESULTS: Simulations of the RF coil characteristics and B 1 + transmit efficiencies agreed well with corresponding experimentally determined parameters. Overall, the RF coil transmit efficiency was, as expected, higher when the gap between the shield and coil increased. The calculated intrinsic SNR showed that maximum SNR would be obtained for a cylindrical shield of diameter 310 mm with an inner diameter of the magnet of 320 mm (assuming 10 mm for the gradient coils). CONCLUSION: This work presents an overview of the trade-offs in transmit efficiencies for RF coils used for POC MRI neuroimaging as a function of coil-to-shield distance and inner diameter of the Halbach magnet. Results show that there is a relatively shallow optimum between a magnet diameter of 290 and 330 mm, with values falling more than 10% if either smaller or larger magnets are used.

The evolution and functional significance of the programmed ribosomal frameshift in prfB.

Release Factor 2 (RF2) is one of two peptide release factors that terminate translation in bacteria. In Escherichia coli, the gene encoding RF2, prfB, contains an in-frame premature RF2-specific stop codon. Therefore, a programmed ribosomal frameshift is required to translate full-length RF2. Here, we investigate the diversity of prfB frameshifting through bioinformatic analyses of >12,000 genomes. We present evidence that prfB frameshifting autoregulates RF2 levels throughout the bacterial domain since (i) the prfB in-frame stop codon is always TGA or TAA, both of which are recognized by RF2, and never the RF1-specific TAG stop codon, and (ii) species that lack the autoregulatory programmed frameshift likely need higher RF2 levels since, on average, they have significantly higher RF2-specific stop codon usage. Overexpression of prfB without the autoregulatory frameshift motif is toxic to Bacillus subtilis, an organism with intermediate RF2-specific stop codon usage. We did not detect the programmed frameshift in any Actinobacteriota. Consistent with this finding, we observed very low frameshift efficiency at the prfB frameshift motif in the Actinobacterium Mycobacterium smegmatis. Our work provides a more complete picture of the evolution of the RF2 programmed frameshifting motif, and its usage to prevent toxic overexpression of RF2.

Quantitative Analysis on Vessel Stiffness and Vector Flow Imaging in the Assessment of Carotid Artery Structural and Functional Changes in Patients With Type 2 Diabetes.

OBJECTIVE: To explore the value of RF-data-based quantitative analysis on vessel stiffness (R-QVS) combined with dynamic vector flow imaging (VFI) in evaluating structural and functional changes in the carotid arteries of patients with type 2 diabetes mellitus (T2DM). METHODS: A prospective study was conducted between October 2022 and April 2024, including 275 consecutive subjects (50 volunteers as controls, 108 patients with T2DM and normal carotid intima-media thickness (CIMT), and 117 patients with T2DM and thickened CIMT). Carotid intima-media thickness (IMT) was measured using real-time intima-media thickness (RIMT) technology, while R-QVS was employed to measure the systolic diameter (Diam), displacement (Dist), hardness coefficient (HC), and pulse wave velocity (PWV) of the distal segment of the carotid artery. VFI was used to measure the maximum wall shear stress (WSSmax), mean wall shear stress (WSSmean), and maximum instantaneous velocity (Vmax) of the vessel wall. Differences in ultrasound parameters among the three groups were compared, and receiver operating characteristic (ROC) curves were plotted to calculate the area under the curve (AUC), evaluating the efficacy of these parameters in assessing structural and functional changes in the carotid arteries of patients with T2DM. RESULTS: There were statistically significant differences in carotid IMT, Diam, Dist, HC, PWV, WSSmax, and Vmax among the three groups (all p < 0.01). The AUCs for evaluating structural and functional changes in the carotid arteries of patients with T2DM using carotid ultrasound parameters Diam, Dist, HC, PWV, WSSmax, and Vmax were 0.64, 0.68, 0.83, 0.88, 0.86, and 0.82, respectively. Multiple linear regression analysis identified Dist., HC, PWV, WSSmax, and WSSmean as influencing factors for CIMT in T2DM patients (with ß values of -0.406, 0.515, 0.564, -0.472, and -0.438, respectively; all p < 0.05). CONCLUSION: R-QVS and VFI techniques contribute to the early assessment of structural and functional changes in the carotid arteries of patients with type 2 diabetes mellitus. Compared with controls, T2DM patients exhibit more advanced functional changes than morphological changes despite normal CIMT. The enhanced sensitivity, reproducibility, and detailed assessment capabilities of these methods make them valuable tools in the early detection and intervention of cardiovascular risk in T2DM.